Hydraulic flow control plate



July 28, 1959 s. E. STEVENS 2,

HYDRAULIC mow CONTROL PLATE Filed Nov. 28, 1956 lf l'32 I l: ./28

52 40 26 54 I8 3844 58 J i 56 42 Fig. 2

INVENTOR. GEORGE E. STEVENS United States Pa HYDRAULIC FLOW CONTROLPLATE George E. Stevens, Watertown, Mass. Application November 28, 1956,Serial No. 624,771

4 Claims. (Cl. 11542) This invention relates to boats having screw typepropellets at the stern ends of the vessels and more particularly tohoods or plates mounted at the propellers for improving control and.operation of boats.

In the operation 'of motor boats propelled from the stern, the bow tendsto rise and the stem to settle deeper into the water in increasingproportions as the thrust exerted by the propeller and speed of the boatincreases. As this condition becomes more pronounced, it results inseveral undesirable characteristics. It makes the boat more sensitive topounding of the waves, increases the pitching of the boat so as togenerally increase the roughness of the ride. Another undesirable resultis that the boat becomes less maneuverable in that side slip of the boatduring a turn is increased so as to make controlled turning morediflicult.

Pursuant to the present invention, these undesirable characteristicshave been overcome and other desirable features and advantages have beenachieved. Among the other features and advantages achieved by thepresent invention is an improvement in maneuverability and steeringcharacteristics at all speeds of boat travel. At low speeds as well ashigh speeds, the boat can be turned with less side slip and greaterprecision. Another advantage is that of improving utilization ofpropulsive power of the propeller.

Accordingly a primary object of the present invention is the provisionof a propeller hood which tends to keep the boat on an even keel at allspeeds of travel.

Another object is the provision of a propeller hood 7 which provides astern lifting force which is sufficient to counteract the prow liftingforce by the water as the speed of the boat increases.

A further object is the provision of a propeller hood which cooperateswith the rudder to increase directional response of the boat to therudder.

A still further object is the provision of a propeller hood whichincreases thrust efficiency of the propeller.

And another object is the provision of a propeller hood which protectsthe propeller from contact with foreign objects and can withstand heavyimpact without injury to the boat hull.

And a further object is the provision of an extremely simple propellerhood structure which is both relatively inexpensive to manufacture andto install at the propeller.

These features, objects and advantages are achieved generally byproviding a cylindrical plate section in proximate relation to and abovethe propeller blades: with the axis of the hood tilted to provide liftfor the stern during forward motion of the boat.

By placing the hood substantially in line with the apex of the prow ofthe boat, a proper transverse direction of the hood for the desiredamount of lift at the stem is achieved.

By providing a spacer between the hood and keel and bolts passingthrough the hood, spacer and keel, very Patented July 28, 1959 ruggedmounting is achieved which can withstand heavy shock loads withoutdamage to the boat hull.

By providing a brace along each end of the hood and fixed to the sidesof the keel, further rigidity of the hood is achieved as well asadditional protective shielding for the propeller.

These and other features, objects and advantages will become moreapparent from the following description taken in connection with theaccompanying drawings of a preferred embodiment of the invention andwherein:

Fig. 1 is a side view of a portion of a'boat with a propeller hood inaccordance with the present invention;

Fig. 2 is an end view taken on the line 2-2 of Fig. 1 to moreclearlyshow construction of the propeller hood.

Referring to Fig. 1 in more detail, a boat incorporating the presentinvention, only segments ofwhich appear in the drawing, is designatedgenerally by the numeral 10. At the stern end 12 of the boat 10ismounted a conventional propeller 14 having a drive shaft 16 passingthrough a sleeve 18 into the hull of the boat for engagement with aconventional driving motor (not shown). To the rear of the propeller 14is a conventional rudder 20 mounted to a rudder shaft 22, the bottomend. ofwhich may, if desired, be pivotally anchored in a keel extension24.

The upper end of the rudder shaft 22may pass upwardly the spacer 28 andkeel planking 34 of the boat 10. The

hood 26 may be further anchored in place by a pair of bars36 and 38, oneat each side of the hood 26. Each of the bars 36 and 38 may be anchoredat one end to the "hood '26 and at the other end tothe boat keel 40 asby screws 42. The bars 36 and 38 may be of rectangular cross section andpreferably bent and twisted so that the body portion 44 between each ofthe ends lies at right angles to the ends and parallel to the top 46 ofthe hood 26. The top 46 of the hood 26 is in transverse relation to theaxis of the shaft 16 and is preferably on a line 47 running to apex 48of prow 50 of the boat 10.

Referring to Fig. 2, assuming the propeller rotates in a clockwisedirection as shown by the arrow 52, the side of the hood 54 on theuprnoving side of the propeller 14 is preferably below the centerline 56of the propeller 14. The other side 58 of the hood 26 which is on thedown moving side of the propeller 14 may be above the centerline 56.

' The hood 26 is found to operate best when its front ends 60 precedesthe propeller 14 to about the front end 62 of the propeller hub 64. Thehood 26 also preferably has a length 66 approximately equal to thediameter 68 of the hood 26. Also, it is important to the properoperation of applicants hood that the back end 70 of the hood 26terminate before it reaches the rudder 20.

In operation of the boat 10, during rotation of the propeller 14 in thedirection 52, the hood 26 will tend to cause a maximum amount of waterto move axially of the propeller 14 so as to increase the thrustgenerating efficiency of the propeller 14. During forward motion of theboat 10, the hood 26 will also tend to lift the stern 12 to counteractthe normal tendency for the stem 12 to draw downward while the vessel isunderway. Also, the constraining of the flow of the water from thepropeller 12 in the direction axially of the shaft 16 and hood 26 in thedirection of the rudder 20- has the effect of improving the steeringqualities of the boat 10 even at low forward speeds.

This invention is not limited to the specific details of thestern of theboat; the flow control plate having substantially the shape of a portionof a cylinder over said propeller, including two curved sides, a frontand back ends, the curved sides of the plate circumscribing thepropeller to substantially a horizontal plane through the axis of thepropeller, the front end of the plate extending forward of the propellerand the back end extending rear ward of the propeller and terminating atthe rudder, a brace at each side of the plate fixed to the plate and thekeel, said plate being tilted diagonally to said boat on a line with theapex of the prow and having an area proportioned for providingsubstantial hydraulic stern lift during forward motion of the boat.

2. A hydraulic flow control plate for a boat having a prow with an apexat the extreme forward end of the boat, a keel plank centrally thereof,a propeller and a rudder behind the propeller at the stern of the boat;the flow control plate comprising a plate in the form of a half cylinderof revolution with a radius about one tenth larger than the radius ofthe propeller radius and a length approximately equal to twice theradius of the plate; said plate including a front end extending forwardof the propeller and a back end terminating at the rudder; mountingmeans rigidly fixing said plate to said boat at an angle such that theplate is substantially on a line with the apex of the prow.

3. A hydraulic flow control plate for a boat having a prow with an apexat the front end, a keel centrally thereof, a propeller and a rudderbehind the propeller at the stern of the boat; the flow control platecomprising a plate in the form of a portion of a cylinder of revolutionwith a radius slightly larger than the radius of the propeller and alength equal to substantially twice the radius of the plate; said platehaving a front and back ends, two sides and a top; the front endextending for- Ward of the propeller and the back end terminating on thepropeller side of the rudder; one of the plate sides extending below thecenter line of the propeller and the other plate side above thecenterline of the propeller; a spacer between the keel and plate foranchoring the plate to the boat; the plate being against the spacer anddiagonally to the boat on a line with the apex of the prow; a pair ofbolts through the keel, spacer and the plate for rigidly fixing theplate and spacer in place; and a brace at each side of the plate fixedto the respective plate side and the boat.

4. A hydraulic flow control plate providing stern lift tending tomaintain level movement with respect to the water line during forwardmotion of a boat having a propeller at the stern of the boat, said flowcontrol plate being fixed over the propeller of the boat and having ahydraulic deflecting surface substantially the shape of a portion of acylinder with a front and back ends and a. length therebetween, thefront end extending forward of the propeller and the back end extendingrearward of the propeller and below the front end so that the lengththerebetween is at an angle with respect to the water line, said angleand length being proportioned for causing said stern lift. 1

References Cited in the file of this patent V UNITED STATES PATENTS436,817 lWelch Septi'23, 1890 904,313 Davis Nov. 17, 1908 983,587Watkins Feb. 7, 1911 2,306,840 Waterval Dec. 29, 1942 7 2,784,691MacMillan Mars 12, 1957 FOREIGN PATENTS 762,747 France Ian. 29, 1934

